/*
 * Copyright 2012-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.spring.initializr.generator.version;

import io.spring.initializr.generator.version.Version.Format;

import org.springframework.util.Assert;

/**
 * 定义一个{@link Version}范围。方括号“[”或“]”表示包含在内的结束
 * 范围和一个圆括号“(”或“)”表示范围的独占结束。一个范围，也可以通过定义一个单一的{@link Version}来解除限制 见下面的例子:
 *
 * <ul>
 * <li>"[1.2.0.RELEASE,1.3.0.RELEASE)" version 1.2.0 and any version after this, up to,
 * but not including, version 1.3.0.</li>
 * <li>"(2.0.0,3.2.0]" any version after 2.0.0 up to and including version 3.2.0.</li>
 * <li>"2.5.0-M1", the first milestone of 2.5.0 and any version after that.</li>
 * </ul>
 *
 * @author Stephane Nicoll
 */
public class VersionRange {

	private final Version lowerVersion;

	private final boolean lowerInclusive;

	private final Version higherVersion;

	private final boolean higherInclusive;

	protected VersionRange(Version lowerVersion, boolean lowerInclusive, Version higherVersion,
			boolean higherInclusive) {
		this.lowerVersion = lowerVersion;
		this.lowerInclusive = lowerInclusive;
		this.higherVersion = higherVersion;
		this.higherInclusive = higherInclusive;
	}

	public VersionRange(Version startingVersion) {
		this(startingVersion, true, null, false);
	}

	/**
	 * Specify if the {@link Version} matches this range. Returns {@code true} if the
	 * version is contained within this range, {@code false} otherwise.
	 * @param version the version to check
	 * @return {@code true} if the version matches
	 */
	public boolean match(Version version) {
		Assert.notNull(version, "Version must not be null");
		int lower = this.lowerVersion.compareTo(version);
		if (lower > 0) {
			return false;
		}
		else if (!this.lowerInclusive && lower == 0) {
			return false;
		}
		if (this.higherVersion != null) {
			int higher = this.higherVersion.compareTo(version);
			if (higher < 0) {
				return false;
			}
			else if (!this.higherInclusive && higher == 0) {
				return false;
			}
		}
		return true;
	}

	/**
	 * Format this version range to the specified {@link Format}.
	 * @param format the version format to use
	 * @return a version range whose boundaries are compliant with the specified format.
	 */
	public VersionRange format(Format format) {
		Version lower = this.lowerVersion.format(format);
		Version higher = (this.higherVersion != null) ? this.higherVersion.format(format) : null;
		return new VersionRange(lower, this.lowerInclusive, higher, this.higherInclusive);
	}

	public Version getLowerVersion() {
		return this.lowerVersion;
	}

	public boolean isLowerInclusive() {
		return this.lowerInclusive;
	}

	public Version getHigherVersion() {
		return this.higherVersion;
	}

	public boolean isHigherInclusive() {
		return this.higherInclusive;
	}

	public String toRangeString() {
		StringBuilder sb = new StringBuilder();
		if (this.lowerVersion == null && this.higherVersion == null) {
			return "";
		}
		if (this.higherVersion != null) {
			sb.append(this.lowerInclusive ? "[" : "(").append(this.lowerVersion).append(",").append(this.higherVersion)
					.append(this.higherInclusive ? "]" : ")");
		}
		else {
			sb.append(this.lowerVersion);
		}
		return sb.toString();
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj) {
			return true;
		}
		if (obj == null) {
			return false;
		}
		if (getClass() != obj.getClass()) {
			return false;
		}
		VersionRange other = (VersionRange) obj;
		if (this.higherInclusive != other.higherInclusive) {
			return false;
		}
		if (this.higherVersion == null) {
			if (other.higherVersion != null) {
				return false;
			}
		}
		else if (!this.higherVersion.equals(other.higherVersion)) {
			return false;
		}
		if (this.lowerInclusive != other.lowerInclusive) {
			return false;
		}
		if (this.lowerVersion == null) {
			if (other.lowerVersion != null) {
				return false;
			}
		}
		else if (!this.lowerVersion.equals(other.lowerVersion)) {
			return false;
		}
		return true;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + (this.higherInclusive ? 1231 : 1237);
		result = prime * result + ((this.higherVersion == null) ? 0 : this.higherVersion.hashCode());
		result = prime * result + (this.lowerInclusive ? 1231 : 1237);
		result = prime * result + ((this.lowerVersion == null) ? 0 : this.lowerVersion.hashCode());
		return result;
	}

	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder();
		if (this.lowerVersion != null) {
			sb.append(this.lowerInclusive ? ">=" : ">").append(this.lowerVersion);
		}
		if (this.higherVersion != null) {
			sb.append(" and ").append(this.higherInclusive ? "<=" : "<").append(this.higherVersion);
		}
		return sb.toString();
	}

}
